Class 10 > Science

Question

An electric bulb is rated 220 V and 100 W. When it is operated on 110 V, the power consumed will be
Medium

Solution

(d)25 W

As we know that the energy consumed by bulb ⇒P= V²/R ⇒R = V²/P where, V= 220volt and P= 100watt R= (220)²/100 =484omega The resistance of the bulb remains constant if the supply voltage is reduced to 110 V. If the bulb is operated on 110V, then the energy consumed by it is given by the expression for power P = V²/R = (110)²/484 = 12100/484 = 25W

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